[GRASS-user] Splitting lines by other lines that overlap

Markus Metz markus.metz.giswork at gmail.com
Mon Mar 2 12:42:25 PST 2020


Hi Johannes,

On Fri, Feb 28, 2020 at 4:27 PM Johannes Radinger <
johannesradinger at gmail.com> wrote:
>
> Hi all,
>
> I have two line vectors: LV1) a complete stream network LV2) sections of
the same stream network representing impoundments.
>
> LV2 is a subset of LV1 and fully spatially overlapping. However, the full
stream network consists of polylines with start/end nodes that do not
correspond to the impoundments vector:
>
> LV1 (complete network):
> +-------------------+------------------+
> LV2 (subset with different start/end nodes)
>      +---+               +-------------+
>
> So how can I get the information of impoundments (LV2) into the attribute
table of the first line vector (LV1). A way that came into my mind but
which is somehow cumbersome:
>
> 1) Extract the start/end node coordinates each impoundment (LV2) using
v.to.db
> 2) Use these coordinates in v.edit to break the river network (LV1)
> 3) Add new categories in layer 2 of LV1 and add an attribute table
> 4) Use v.distance to query the information from LV2 and copy it to the
corresponding new reaches in LV1
> ..This is not yet tested and not the most straight forward way.
>
> All this I guess would be easier if there would be something like
v.overlay that works with two line vectors...

The only alternative I can think of is v.clean tool=break errors=nodes, but
this might not be exactly what you need: start/end nodes from LV2 might be
missing if there are matching nodes in LV1. Your approach seems to be
reasonable, even if it involves several steps.

Markus M

>
> Has anybody done similar analysis in GRASS so far?
>
> cheers,
> Johannes
>
> tart/end nodes of the
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